1. Field of the Invention
This invention relates to organosilicon compounds, to anti-corrosion and/or adhesion promoting coating compositions made therefrom and methods for their application to metals and to metals possessing anti-corrosion and/or adhesion promoting coatings based on organosilicon compounds.
2. Description of the Prior Art
Most metals are susceptible to some form of corrosion, in particular atmospheric corrosion, resulting in the formation of various types of rust. Such corrosion may significantly affect the quality of a metal. Although superficial corrosion can usually be removed from metal surfaces, processes for its removal tend to be time consuming, costly and may have a negative impact on the integrity of the metal. Where coatings are applied to metal surfaces, corrosion of the metal may result in inadequate or ineffective adhesion between the coating and the metal surface. A reduction in adhesion between a coating and metal surface to which the coating has been applied may likewise lead to corrosion of the metal.
Metals of many kinds, including metal alloys, metal laminates, metal composites, and, the like, are widely used in manufacturing and construction. Certain types of metal, particularly ferrous metals such as iron and steel, often develop rust during storage and shipment. Rust (also called “storage stain”) is typically caused by moisture which condenses on the surface of the metal there to react with the metal or metal coating on the metal. Rust is aesthetically unappealing and often impairs the ability of the metal to directly undergo subsequent processing operations. Thus, prior to conducting any subsequent processing operations, rust often needs to be removed from the surface of metal and the metal surface treated to prevent rust from reforming. Various methods are currently employed to not only prevent the formation of rust during shipment and storage, but also to prevent the formation of rust after the metal has undergone subsequent processing operations.
It is well known that prevention of rust on metals during their storage, shipping and use can be achieved by applying to their surfaces a thin film such as one of chromate. While chromate coatings do provide resistance to the formation of rust, chromium is highly toxic and environmentally undesirable. Furthermore, a chromium layer will not necessarily improve the adhesion of any subsequent layer applied thereto.
The rusting of metal can also be prevented or inhibited during storage, shipment and use by applying an aqueous solution of a hydrolyzable silane to the surface of the metal and thereafter curing the silane to provide a durable, adherent protective coating. Such a coating, however, may generate one or more volatile organic compounds (VOCs) and/or Hazardous Air Pollutants (HAPs) during hydrolysis of the silane. VOCs and HAPs are environmentally undesirable and governmental agencies have implemented regulations intended to limit the amounts of VOCs and HAPs materials. These regulations often require the purchase, installation and maintenance of expensive air purification equipment. Exposure to VOCs and HAPs can also be detrimental to the health and safety of workers due to their potential toxicity and flammability.
Therefore, there exists a need for a coating composition and a coating method for the protective treatment of metals that does not utilize chromium and that generates essentially no, or at most, very little VOCs or HAPs while still imparting desirable anti-corrosion and adhesion properties to the treated metals.